PURPOSE: To send a synchronizing signal for a long range through an inexpensive transmission line by providing a decoding circuit decoding a switching signal from two received signals or over and a circuit generating a new synchronizing signal based on the decoded signal to the controller for terminal equipment.

CONSTITUTION: An external synchronizing signal generator 14 is provided with a frequency divider circuit 24 generating switching signal and 1st and 2nd low frequency signals, a changeover circuit 26, and an output circuit 28 sending the signals to a television camera 16 through a cable 20. The television camera 16 is provided with a demodulation circuit 30, a timing signal generating circuit 32, and an internal synchronizing signal generating circuit 34. Let the frequency of a vertical synchronizing signal of the television camera 16 be f0, a frequency of a switching signal be f1, 1st and 2nd frequencies be f2, f3 respectively and a frequency of a clock signal be f4, and n1, n2, n3, n4 be an optional integer being 1 over, then the frequencies are selected to be f1=f0÷2n1, f2=f1×2n2, f3=f2×2n3, and f4=f3×2n4. Thus, the 1st and 2nd low frequency signals can be sent through an inexpensive cable such as a twisted pair cable.